Dynamic Range improvement.

For some time I’ve been using a discone antenna a few metres above the house roof with around 15m of good quality coax feeding a Pro Stick Plus with reasonable but not great results.
I recently decided to upgrade, replacing the discone with a FlightAware aerial and a Rtl SDR-Radio Blog filtered LNA a few metres from the antenna. The original 15m coax still delivers the amplified signals to the receiver.

First of all the Pro stick plus had to go as its internal LNA was now being swamped with too much signal, so my RTL V3 dongle took its place with some improvement.
Despite running the dongle at 0db gain, aircraft taking off a few miles away were still dropping out so this was eventually fixed by inserting a 20db attenuator at the dongle end of the coax.

The system is working fine and is much better than the original setup, but there is clearly a trade off between reliable decoding of strong local signals and getting higher message counts with longer range which is presumably down to the dynamic range the dongle is capable of handling.

I wonder if anyone has progressed to alternatives such as the Airspy and managed better local and distant reception.

Omni directional antennas always perform better further away, due to a donut effect those overhead will always be effected.
Either by overloading if the device is made too sensitive, or weak signal due to the lateral propagation

Posts not to be taken as official support representation - Just a helpful uploader who tinkers

My guess would be that somehow adjusting the gain didn't work, reducing the gain to 0 should be enough attenuation.
Maybe there is something overloaded before the gain is applied, that's possible but i doubt it.

I'm using Dump1090 1.15~dev and I did wonder why dropping the original gain setting of 49.6 down gradually to zero didn't really seem to be having the expected effect.

The LNA allegedly provides around 27dB gain and at present I am using 3.3V from the Raspberry Pi to power it. I experimented with lower voltage levels to reduce the LNA gain but gave up and inserted the attenuator instead.

I'm guessing the upgrade overall might have increased the signal levels by something around 30dB and I would have thought that after losing the internal LNA of the Pro Stick plus, then slightly reducing the --gain setting in the replacement dongle would have been about right.

It does seem absurd to have to use an attenuator in the feed while the dongle is supposedly set to 0dB gain.

For the record I set the gain in the Fr24 Feeder Settings webpage, "Process Arguments" with a value of --gain 0.0
Just tried varying the gain a few times and it doesn't seem to be having any effect that I can see!

I’m still very happy at the moment with the package of Dump1090 1.15 which includes the performance graphs, as scripted by J Prochazka.
However I just got hold of another rpi 3b+ so I am now tempted to try out the goodies on offer from wiedehopf.